change:
initYandexMaps(res.geoObjects.get(0).geometry.getCoordinates());
to:
{% load l10n %}
{% if object.lat and object.lng %}
initYandexMaps([{{ object.lat|unlocalize }}, {{ object.lng|unlocalize }}]);
{% else %}
initYandexMaps(res.geoObjects.get(0).geometry.getCoordinates());
{% endif %}